JP7522305B2 - Monoazo dichroic dye compound, polarizing plate composition containing the same, polarizing plate formed therefrom, and optical element including the same - Google Patents

Description

The present invention relates to a dichroic dye compound that is mixed with a liquid crystal compound to form a polarizing plate, a polarizing plate composition containing the same, a polarizing plate formed from the same, and an optical element including the same.
This application claims priority to Korean Patent Application No. 10-2020-0181624, filed on December 23, 2020, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings.

2. Description of the Related Art Polarizing plates are used in optical elements such as liquid crystal displays and organic light emitting diodes to control optical activity or birefringence, or to prevent external light reflection.
Generally, polarizing plates used are those in which iodine is adsorbed and oriented as a polarizing substance on a polarizing film substrate made of stretch-oriented polyvinyl alcohol or its derivatives, or those formed by mixing a dichroic dye with a liquid crystal compound.

Iodine-based polarizing plates, which use iodine as a polarizing plate (polarizing element), have excellent initial polarizing performance in the visible light range, but have very poor polarizing performance in the near-ultraviolet range, are vulnerable to water and heat, and have durability problems when used for long periods of time under high temperature and high humidity conditions.

Dye-based polarizers, which use dichroic dye compounds as polarizing materials, generally have better durability under high temperature and humidity conditions than iodine-based polarizers, and are therefore used in areas that require high heat resistance and durability, such as car dashboards, airplanes, and LCD projectors. However, even in these cases, there are limitations to heat resistance and durability depending on the dye and polymer material used.

On the other hand, the bisazo dye compounds used as the polarizing material in dye-based polarizing plates have the disadvantages of a complicated synthesis process and low yield.

A first object of the present invention is to provide a monoazo dichroic dye compound which has good dichroism, excellent heat resistance and light resistance, and can be effectively used in a dye-based polarizing plate.
A second object of the present invention is to provide a polarizing plate composition having the above-mentioned properties and a polarizing plate formed therefrom.
A third object of the present invention is to provide an optical element including a polarizing plate having the above-mentioned characteristics.

In order to solve the above-mentioned technical problems, according to a first embodiment of the present invention, there is provided a monoazo dichroic dye compound represented by the following chemical formula 1:

In Chemical Formula 1,
R ₁ is any one selected from the group consisting of a substituted or unsubstituted aryl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; any one group selected from the group consisting of NR ₄ OH; NHR ₅ ; NR ₆ ; OR ₇ ; COOR ₈ ; OCOR ₉ ; SR ₁₀ ; a halogen group; OH; CN; COOH; PO ₃ ; SO ₃ ; and NO ₂ , and R ₄ to R ₁₀ are any one selected from the group consisting of a hydrogen atom, an alkoxy group, and an alkoxyalkyl group, each having 1 to 20 carbon atoms; any one of a halogen atom or an alkyl group containing a halogen atom; and any one of a heterocyclic group or an aryl group substituted or unsubstituted with one or more selected from the group consisting of an alkoxy group, an alkoxyalkyl group, a halogen, and an alkyl group;
R ₂ is independently any one selected from the group consisting of hydrogen; a substituted or unsubstituted aryl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; NR ₄ OH; NHR ₅ ; NR ₆ ; OR ₇ ; COOR ₈ ; OCOR ₉ ; SR ₁₀ ; a halogen group; OH; CN; COOH; PO ₃ ; SO ₃ ; and NO ₂ , wherein R ₄ to R ₁₀ are independently any one selected from the group consisting of a hydrogen atom, an alkoxy group, and an alkoxyalkyl group; a halogen atom or an alkyl group containing a halogen atom; and a heterocyclic group or an aryl group substituted or unsubstituted with one or more selected from the group consisting of an alkoxy group, an alkoxyalkyl group, a halogen, and an alkyl group;
_X1 and _X2 are each independently any one selected from the group consisting of N, S, O and C;
_Y1 and _Y2 are each independently any one selected from the group consisting of C, S, O, and N;
_R3 is a substituted or unsubstituted heterocyclic group having 1 to 20 carbon atoms.

According to a second embodiment of the present invention, in the first embodiment,
The R ₁ may be any one selected from the group consisting of CN, OH, NHR ₅ , NR ₆ , OR ₇ , and COOR ₈ , and R ₂ may be any one selected from the group consisting of hydrogen, CN, OH, NHR ₅ , NR ₆ , OR ₇ , and COOR _8. More specifically, the R ₁ may be any one selected from the group consisting of _{NHR 5 ,} NR 6 , OR ₇ , and COOR ₈ , and R ₂ may be any one selected from the group consisting of hydrogen, NHR ₅ , NR ₆ , OR ₇ , and COOR _8. Most specifically, the R ₁ may be NR ₆ or OR ₇ , and R ₂ may be any one selected from the group consisting of hydrogen, OR ₇ , and COOR ₈ .

According to a third embodiment of the present invention, in the first or second embodiment, _X1 and _X2 may each be independently selected from N or C.

According to a fourth embodiment of the present invention, in any one or more of the first to third embodiments, _Y1 and _Y2 may be independently selected from S or O.

According to a fifth embodiment of the present invention, in any one or more of the first to fourth embodiments, _R3 may be any one selected from the group consisting of barbituric acid, hydantoin, 3-thiohydantoin, 1,3-indandione, and dihydrouracil, which are substituted or unsubstituted with any one or more selected from the group consisting of alkyl groups, arylalkyl groups, aryl groups, halogen groups, alkoxy groups, alkoxyalkyl groups, alkoxyaryl groups, nitro groups, cyano groups, carboxyl groups, and amide groups. More specifically, _R3 may be any one selected from the group consisting of barbituric acid, hydantoin, and 3-thiohydantoin, which are substituted or unsubstituted with any one or more selected from the group consisting of alkyl groups, arylalkyl groups, and aryl groups.

The present invention provides a polarizing plate composition in which a monoazo dichroic dye compound is mixed with a liquid crystal compound, and a polarizing plate formed by curing the composition, which is one or more of the first to fifth embodiments. The dichroic ratio (DO) of the polarizing plate may be 19 to 25, the heat resistance (Δintensity) of the polarizing plate may be 6% or less, and the light resistance (Δintensity) of the polarizing plate may be 3% or less.
The present invention also provides an optical element comprising a polarizing plate formed as described above.

The dichroic dye compound of the present invention is a monoazo type dichroic dye compound represented by Chemical Formula 1, and has good dichroic properties and excellent heat resistance and light resistance, and therefore has good durability even when produced or used under harsh conditions.
In addition, they have the advantage of being easier to synthesize and of being higher in yield than bisazo-type dichroic dye compounds.

The present invention will be described in detail below. The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary and dictionary meanings, but should be interpreted in a meaning and concept that corresponds to the technical idea of the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of the term in order to best describe the invention.

The monoazo dichroic dye compound of the present invention is represented by the following chemical formula 1, and is a monoazo compound having an azo group on only one side.

In Chemical Formula 1,
R ₁ is any one selected from the group consisting of a substituted or unsubstituted aryl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; any one group selected from the group consisting of NR ₄ OH; NHR ₅ ; NR ₆ ; OR ₇ ; COOR ₈ ; OCOR ₉ ; SR ₁₀ ; a halogen group; OH; CN; COOH; PO ₃ ; SO ₃ ; and NO ₂ , and R ₄ to R ₁₀ are any one selected from the group consisting of a hydrogen atom, an alkoxy group, and an alkoxyalkyl group, each having 1 to 20 carbon atoms; any one of a halogen atom or an alkyl group containing a halogen atom; and any one of a heterocyclic group or an aryl group substituted or unsubstituted with one or more selected from the group consisting of an alkoxy group, an alkoxyalkyl group, a halogen, and an alkyl group;
R ₂ is independently any one selected from the group consisting of hydrogen; a substituted or unsubstituted aryl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; NR ₄ OH; NHR ₅ ; NR ₆ ; OR ₇ ; COOR ₈ ; OCOR ₉ ; SR ₁₀ ; a halogen group; OH; CN; COOH; PO ₃ ; SO ₃ ; and NO ₂ , wherein R ₄ to R ₁₀ are independently any one selected from the group consisting of a hydrogen atom, an alkoxy group, and an alkoxyalkyl group; a halogen atom or an alkyl group containing a halogen atom; and a heterocyclic group or an aryl group substituted or unsubstituted with one or more selected from the group consisting of an alkoxy group, an alkoxyalkyl group, a halogen, and an alkyl group;
_X1 and _X2 are each independently any one selected from the group consisting of N, S, O and C;
_Y1 and _Y2 are each independently any one selected from the group consisting of C, S, O, and N;
_R3 is a substituted or unsubstituted heterocyclic group having 1 to 20 carbon atoms.

As mentioned above, bisazo-type dichroic dye compounds are known to have very low yields because the synthesis process is not easy. The dichroic dye compound of the present invention is a monoazo-type compound, so the synthesis process is relatively easy and the yield is improved. In addition, despite being a monoazo-type compound, it has good dichroism and excellent heat resistance and light resistance.

[R ₁ and R ₂ in Chemical Formula 1]
R ₁ is any one selected from the group consisting of a substituted or unsubstituted aryl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; any one group selected from the group consisting of NR ₄ OH; NHR ₅ ; NR ₆ ; OR ₇ ; COOR ₈ ; OCOR ₉ ; SR ₁₀ ; a halogen group; OH; CN; COOH; PO ₃ ; SO ₃ ; and NO ₂ , and R ₄ to R ₁₀ each have 1 to 20 carbon atoms and are each independently any one selected from the group consisting of a hydrogen atom, an alkoxy group, and an alkoxyalkyl group; any one of a halogen atom or an alkyl group containing a halogen atom; and any one of a heterocyclic group or an aryl group substituted or unsubstituted with one or more selected from the group consisting of an alkoxy group, an alkoxyalkyl group, a halogen, and an alkyl group.

R ₂ is independently any one selected from the group consisting of hydrogen; a substituted or unsubstituted aryl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; NR ₄ OH; NHR ₅ ; NR ₆ ; OR ₇ ; COOR ₈ ; OCOR ₉ ; SR ₁₀ ; a halogen group; OH; CN; COOH; PO ₃ ; SO ₃ ; and NO ₂ , and R ₄ to R ₁₀ are independently any one selected from the group consisting of a hydrogen atom, an alkoxy group, and an alkoxyalkyl group; a halogen atom or an alkyl group containing a halogen atom; and a heterocyclic group or an aryl group substituted or unsubstituted with one or more selected from the group consisting of an alkoxy group, an alkoxyalkyl group, a halogen, and an alkyl group.

In the case of _R1 and _R2 "any one selected from the group consisting of a substituted or unsubstituted aryl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms", the term "substituted" includes the fact that the aryl group, the heteroaryl group, or the alkyl group is substituted with, for example, any one or more selected from the group consisting of an alkoxy group, an alkoxyalkyl group, a halogen, and an alkyl group.

_R1 may be any one selected from the group consisting of CN, OH, _NHR5 , _NR6 , _OR7 , and _COOR8 , and _R2 may be any one selected from the group consisting of hydrogen, CN, OH, _NHR5 , _NR6 , _OR7 , and _COOR8 .
More specifically, R ₁ may be any one selected from the group consisting of NHR ₅ , NR ₆ , OR ₇ , and COOR ₈ , and R ₂ may be any one selected from the group consisting of hydrogen, NHR ₅ , NR ₆ , OR ₇ , and COOR ₈ .
Most specifically, R ₁ may be NR ₆ or OR ₇ , and R ₂ may be any one selected from the group consisting of hydrogen, OR ₇ , and COOR ₈ .

[ _X1 and _X2 in Chemical Formula 1]
_X1 and _X2 are each independently any one selected from the group consisting of N, S, O and C.
More specifically, _X1 and _X2 may each be independently selected from N or C.

[ _Y1 and _Y2 in Chemical Formula 1]
_Y1 and _Y2 are each independently any one selected from the group consisting of C, S, O and N.
More specifically, _Y1 and _Y2 may each be independently selected from S or O.

[R ₃ in Chemical Formula 1]
_R3 is a substituted or unsubstituted heterocyclic group having 1 to 20 carbon atoms.
The heterocycle has a rigid structure, and therefore contributes to improving the heat resistance and light fastness of the monoazo dichroic dye compound of Chemical Formula 1.
Specifically, _R3 may be any one selected from the group consisting of barbituric acid, hydantoin, 3-thiohydantoin, 1,3-indandione, and dihydrouracil, which are substituted or unsubstituted with at least one selected from the group consisting of an alkyl group, an arylalkyl group, an aryl group, a halogen group, an alkoxy group, an alkoxyalkyl group, an alkoxyaryl group, a nitro group, a cyano group, a carboxyl group, and an amide group. More specifically, _R3 may be any one selected from the group consisting of barbituric acid, hydantoin, and 3-thiohydantoin, which are substituted or unsubstituted with at least one selected from the group consisting of an alkyl group, an arylalkyl group, and an aryl group.

The monoazo dichroic dye compound of Chemical Formula 1 may be, most specifically, any one of the compounds represented by the following formulas:

The monoazo dichroic dye compound of the above-mentioned chemical formula 1 can be synthesized by combining known organic synthetic chemistry methods.

For example, they can be synthesized using known methods by referring to texts such as Dichroic Dyes for Liquid Crystal Display (A.V. Lvashchenko, CRC, 1994).

The monoazo dichroic dye compound of the present invention described above is combined with a liquid crystal compound to form a polarizing plate composition, which is then cured to form a polarizing plate. In other words, by combining the monoazo dichroic dye compound of the present invention with a liquid crystal compound, the dichroic dye compound can be oriented with a high degree of orientation while suppressing precipitation of the dichroic dye compound.

As the liquid crystal compound contained in the polarizing plate composition of the present invention, any of the known low molecular weight liquid crystal compounds and polymeric liquid crystal compounds can be used. Here, "low molecular weight liquid crystal compound" means a liquid crystal compound that does not have repeating units in its chemical structure. Also, "polymeric liquid crystal compound" means a liquid crystal compound that has repeating units in its chemical structure. For example, a curable liquid crystal compound can be used to improve the alignment of a dichroic dye compound, and a specific example thereof is 4-(3-acryloyloxy-propoxy)benzoic acid o-tolyl ester.

In the polarizing plate composition of the present invention, the monoazo dichroic dye compound of Chemical Formula 1 may be contained in an amount of, for example, 2 to 40 wt % based on the total weight of the solid content of the polarizing plate composition, but is not limited thereto.

When the polarizing film composition is formulated, a mixture of a red dichroic dye, a blue dichroic dye, and a green dichroic dye, or a dichroic dye having a structure that exhibits red dichroism, a structure that exhibits blue dichroism, and a structure that exhibits green dichroism, may be added as necessary, and a polarizing plate to which such a mixture of dichroic dyes is applied can linearly polarize all light in the visible light range. In addition, for color correction, dichroic dyes of other colors besides red, green, and blue, or dichroic dyes having a structure that exhibits dichroism of other colors besides red, green, and blue, may be formulated in the polarizing plate composition. When red, blue, green, and color correction dichroic dyes are used, they may be formulated in any ratio depending on the absorption wavelength of the substance, and the blending ratio is not limited.

Examples of other additives include, but are not limited to, catalysts, sensitizers, stabilizers, chain transfer agents, inhibitors, accelerators, surface active components, lubricants, wetting agents, dispersants, hydrophobizing agents, adhesives, flow improvers, bubble formation inhibitors, diluents, colorants, dyes or pigments, which are generally known in the art, and these components can be suitably selected and blended as necessary.
The polarizing plate composition may also contain, as necessary, for example, 1 to 10 parts by weight, more preferably 2 to 7 parts by weight, of a curing agent. That is, when the polarizing plate composition is coated on a substrate to form a polarizing plate, if the curing is performed using an electron beam, it is not necessary to add a separate curing agent to the polarizing plate composition, but if the polarizing plate composition needs to be dried by photo-curing or thermal curing after coating, a separate curing agent is added to the polarizing plate composition.

As the curing agent, those generally used in the art can be used, and as the photopolymerization initiator using ultraviolet light, at least one active halogen compound selected from halomethyloxadiazole compounds and halomethyl-s-triazine compounds, 3-aryl-substituted coumarin compounds, benzophenone compounds, acetophenone compounds and derivatives thereof, cyclopentadiene-benzene-iron complexes and salts thereof, and oxime compounds can be used. Examples of active halogen compounds that are halomethyloxadiazole compounds include 2-halomethyl-5-vinyl-1,3,4-oxadiazole compounds, 2-trichloromethyl-5-styryl-1,3,4-oxadiazole, 2-trichloromethyl-5-(p-cyanostyryl)-1,3,4-oxadiazole, and 2-trichloromethyl-5-(p-methoxystyryl)-1,3,4-oxadiazole. Examples of active halogen compounds that are halomethyl-s-triazine compounds include vinyl-halomethyl-s-triazine compounds, 2-(naphth-1-yl)-4,6-bis-halomethyl-s-triazine compounds, and 4-(p-aminophenyl)-2,6-di-halomethyl-s-triazine compounds.

Examples of photopolymerization initiators include the Irgacure (registered trademark) series manufactured by Ciba Specialty Chemicals (e.g., Irgacure 651, Irgacure 184, Irgacure 500, Irgacure 1000, Irgacure 149, Irgacure 819, Irgacure 261), the Darocur (registered trademark) series (e.g., Darocur 1173), 4,4'-bis(diethylamino)-benzophenone, 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione, 1-(O-acetyloxime)-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone, 2-benzyl-2-dimethylamino-4-morpholino-4-methylphenylamine, and 2-benzyl-2-dimethylamino-4-morpholino-4-methylphenylamine. Examples of the curing agent include linobutyrophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-(o-chlorophenyl)-4,5-diphenylimidazolyl dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazolyl dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazolyl dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazolyl dimer, 2-(p-dimethoxyphenyl)-4,5-diphenylimidazolyl dimer, 2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazolyl dimer, 2-(p-methylmercaptophenyl)-4,5-diphenylimidazolyl dimer, and benzoin isopropyl ether. The curing agent can be used alone or in a mixture.

For coating the polarizing plate composition, a suitable solvent may be selected and each component, such as the monoazo dichroic dye compound, may be mixed. The solvent and the solid content of the composition are not particularly limited and may be easily selected and applied by a person skilled in the art in accordance with the purpose of the present invention.

A glass plate or a plastic substrate can be used as the substrate on which the polarizing plate composition is coated to form a polarizing plate. The plastic substrate is not particularly limited, but can be made of acrylic resin, polycarbonate resin, epoxy resin, or polyester resin.

The polarizing plate composition may be applied to the substrate by a thin film coating method commonly used in the art, such as spin coating, blade coating, casting coating, or roll coating. The polarizing plate composition is preferably coated so that the thickness of the final cured polarizing plate is 0.1 microns to 10 microns, preferably 0.3 microns to 7 microns, but is not limited thereto. The curing method for curing the polarizing plate composition after coating it on the substrate may be a known curing method such as electron beam curing, heat curing, or ultraviolet curing, but is not particularly limited thereto.

Meanwhile, when a polarizing plate manufactured using a dichroic dye is used in an LCD (Liquid Crystal Display), the orientation of the coated dichroic dye is important. Therefore, in order to improve the orientation of the dichroic dye, the substrate itself can be given orientation, or a separate orientation film can be formed to give orientation, and then the polarizing plate can be coated with the polarizing plate composition.

Orientation to the substrate can be achieved by forming irregularities on the substrate surface using a rubbing method to give orientability to the molecules forming the coating film. Alternatively, a separate alignment film made of an azo-series compound, polyimide, polyamide, cinnamic acid ester, amide acid, etc. can be formed on the substrate, and alignment can be imparted to the alignment film using a rubbing method or a photo-alignment method. As a non-contact surface treatment method, a photo-alignment film method can be used in which polarized ultraviolet light is irradiated onto a polarizing plate to impart anisotropy to the coating film.

The surface of the polarizing plate formed using the monoazo dichroic dye compound of the present invention may be subjected to post-treatments such as antistatic treatment, corona treatment, hard coating treatment, antireflection treatment, and antiglare treatment, if necessary.

The polarizing plate obtained by the above-mentioned method has a good dichroic ratio and excellent durability under high temperature and high humidity conditions such as heat resistance and light resistance, and is unlikely to discolor or deteriorate in polarization performance, so it can be used in optical elements that require high heat resistance, durability, and polarization performance, such as automobile dashboards, airplanes, and liquid crystal projectors. The dichroic ratio (DO) of such a polarizing plate may be 19 to 25, the heat resistance (Δintensity) of the polarizing plate may be 6% or less, and the light resistance (Δintensity) of the polarizing plate may be 3% or less. The dichroic ratio (DO), heat resistance (Δintensity) of the polarizing plate, and light resistance (Δintensity) of the polarizing plate respectively refer to values measured by the evaluation methods described below in the items of dichroic ratio evaluation, heat resistance evaluation, and light resistance evaluation.

The present invention will now be described in detail with reference to specific examples. However, the examples of the present invention may be modified into many other forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

<Confirmation of compound structure>
The structure of the compound was confirmed by liquid chromatography mass spectrometry (LC-MS). The compound to be measured was dissolved in THF and measured. The measured peak was analyzed to confirm the m/z value.

<Evaluation of Light Fastness>
The light resistance was evaluated by exposing the polarizing plates prepared in the examples and comparative examples to a Red Lenser flash LED LENSER P7R (9408R) at 1000 lm for 1 hour and then measuring the absorbance. The light resistance was evaluated as the difference between the initial absorbance and the absorbance after exposure.
Light resistance (ΔIntensity)=[(absorbance after 1 hour at 1000 lm)−(initial absorbance)]×100(%)

<Evaluation of heat resistance>
The heat resistance was evaluated by measuring the difference between the initial absorbance and the absorbance of the polarizing plates prepared in the Examples and Comparative Examples after they were kept in a thermohygrostat at 80° C. for 250 hours.
Heat resistance (ΔIntensity)=[(absorbance after 250 hours)−(initial absorbance)]×100(%)

<Evaluation of dichroic ratio>
The dichroic ratio was measured by measuring the absorbance in the wavelength region of 550 to 700 nm using a multichannel spectrometer for the polarizing plates produced in the Examples and Comparative Examples with a linear polarizer inserted on the light source side of an optical microscope, and calculating the dichroic ratio using the following formula.
Dichroic ratio (D0) = Az0/Ay0
In the above formula, Az0 represents the absorbance of the light-absorbing polarizing plate with respect to polarized light in the absorption axis direction, and Ay0 represents the absorbance of the polarizing plate in the polarization axis direction.

<Synthesis Example>
Synthesis of intermediate 1-1
Phosphoryl trichloride (1.27 g, 8.3 mmol) was slowly added dropwise to 10 ml of DMF under a nitrogen atmosphere at 0° C., and the mixture was stirred for 1 hour. Thieno[2,3-d]thiazol-2-amine (1 g, 6.4 mmol) was added thereto, and the mixture was heated to 80° C. and stirred to proceed with the reaction. The temperature was then lowered to room temperature, and 30 ml of water was added to terminate the reaction. 30 ml of 1N NaOH was added to the resulting solid, and 50 ml of chloroform was further added to dissolve it, and the solid was washed twice with water, and the organic layer was separated, and anhydrous magnesium sulfate was added, stirred, and filtered, and the filtrate was distilled under reduced pressure. The concentrated compound was purified through a silica column using chloroform and ethyl acetate to produce solid intermediate 1-1 (0.91 g, 77%, MS: [M+H]+=184.0).

Synthesis of intermediate 1-2
At 0°C, intermediate 1-1 (1 g, 5.4 mmol) was added to 3 ml of acetic acid and 7 ml of propionic acid, and the mixture was stirred for 30 minutes. Sodium nitrite (0.39 g, 5.7 mmol) was dissolved in 16 ml of sulfuric acid, and the mixture was slowly added dropwise, and the mixture was stirred for 30 minutes while maintaining the temperature at 5°C or less. N,N-diethylaniline (1.2 g, 8.1 mmol) was dissolved in 5 ml of methanol, and the mixture was slowly added dropwise, and the mixture was stirred for 2 hours. At this time, the mixture was titrated with 2N aqueous sodium acetate solution to maintain the pH at 5-7. After the reaction was completed, the mixture was filtered and washed twice with water and methanol to produce solid intermediate 1-2 (1.4 g, 75%, MS: [M+H]+=345.1).

Synthesis Example 1
Intermediate 1-2 (0.5 g, 1.5 mmol) and imidazoline-2,4-dione (0.16 g, 1.6 mmol) were added to 20 ml of acetic acid. Ammonium acetate (0.2 g, 2.76 mmol) was added to the mixture, and the mixture was refluxed for 6 hours. The temperature of the reaction mixture was lowered to room temperature, and the reaction was terminated using sodium bicarbonate. The mixture was extracted three times using 20 ml of chloroform and 20 ml of water. Water was removed using magnesium sulfate, and the solvent was evaporated. The mixture was purified through a silica column using chloroform and ethyl acetate to produce compound 1 (0.31 g, 50%, MS: [M+H]+=426.1).

Synthesis Example 2
Compound 2 (0.27 g, 41%, MS: [M+H]+=454.1) was produced in the same manner as in Synthesis Example 1, except that 1,3-dimethylimidazoline-2,4-dione was used instead of imidazoline-2,4-dione.

Synthesis Example 3
Compound 3 (0.34 g, 49%, MS: [M+H]+=482.2) was produced in the same manner as in Synthesis Example 1, except that 1,3-diethylimidazoline-2,4-dione was used instead of imidazoline-2,4-dione.

Synthesis Example 4
Compound 4 (0.33 g, 47%, MS: [M+H]+=487.1) was prepared in the same manner as in Synthesis Example 1, except that 1-acetyl-2-thioxo-imidazolin-4-one was used instead of imidazoline-2,4-dione.

Synthesis Example 5
Compound 5 (0.29 g, 44%, MS: [M+H]+=454.1) was prepared in the same manner as in Synthesis Example 1, except that barbituric acid was used instead of imidazoline-2,4-dione.

Synthesis Example 6
Compound 6 (0.37 g, 53%, MS: [M+H]+=483.1) was produced in the same manner as in Synthesis Example 1, except that 1,3-dimethylbarbituric acid was used instead of imidazoline-2,4-dione.

Synthesis Example 7
Compound 7 (0.34 g, 45%, MS: [M+H]+=526.1) was produced in the same manner as in Synthesis Example 1, except that 1,3-diethyl-2-thiobarbituric acid was used instead of imidazoline-2,4-dione.

Synthesis Example 8
Compound 8 (0.31 g, 45%, MS: [M+H]+=472.1) was prepared in the same manner as in Synthesis Example 1, except that 1,3-indandione was used instead of imidazoline-2,4-dione.

Synthesis Example 9
Intermediate 9-1 (1.5 g, 69%, MS: [M+H]+=399.0) was prepared in a similar manner to the synthesis of Intermediate 1-2, except that 1-hexylindoline was used instead of N,N-diethylaniline.
Compound 9 (0.28 g, 46%, MS: [M+H]+=480.1) was produced in the same manner as in Synthesis Example 1, except that Intermediate 9-1 was used instead of Intermediate 1-2.

Synthesis Example 10
Compound 10 (0.55 g, 66%, MS: [M+H]+=660.2) was produced in the same manner as in Synthesis Example 9, except that 1,3-diphenylbarbituric acid was used instead of imidazoline-2,4-dione.

Synthesis Example 11
Compound 11 (0.42 g, 56%, MS: [M+H]+=598.2) was produced in the same manner as in Synthesis Example 9, except that 1-methyl-3-phenylbarbituric acid was used instead of imidazoline-2,4-dione.

Synthesis Example 12
4-Butylaniline (2 g, 13.4 mmol) was added to 10 ml of hydrochloric acid, and 5 ml of aqueous sodium nitrite (1.017 g, 14.7 mmol) solution was added dropwise and stirred for 30 minutes. Then, 0.08 g of sulfamic acid was added and stirred for another 30 minutes. Thieno[2,3-d]thiazol-2-amine (0.3 g, 6.7 mmol) was dissolved in 10 ml of methanol, and slowly added dropwise and stirred for 2 hours. After the reaction was completed, the mixture was washed with 30 ml of methanol and 30 ml of water and filtered to produce intermediate A-1. Solid compound A (0.28 g, 37%, MS: [M+H]+=476.2) was produced in the same manner as in the synthesis of intermediate 1-2, except that A-1 was used instead of intermediate 1-1.

Synthesis Example 13

2-Amino-4-chlorothiazole-5-carbaldehyde (2 g, 12.3 mmol) was added to 10 ml of sulfuric acid, and 5 ml of aqueous sulfuric acid solution of sodium nitrite (1.018 g, 14.8 mmol) was added dropwise and stirred for 30 minutes. Then, 0.08 g of sulfamic acid was added and stirred for another 30 minutes. N,N-diethylaniline (1.1 g, 7.4 mmol) was dissolved in 10 ml of methanol, and then slowly added dropwise and stirred for 2 hours. After the reaction was completed, the mixture was washed with 30 ml of methanol and 30 ml of water and filtered to produce intermediate B-1. Solid compound B (1.33 g, 83%, MS: [M+H]+=521.2) was produced in the same manner as in Synthesis Example 2, except that B-1 was used instead of intermediate 1-2.

<Production of Polarizing Plate>
Production Example 1
A 2 wt % alignment layer forming solution (2 wt % polyacrylate having methoxycinnamic acid (MPN-Ci) as a photosensitive functional group in the side chain dissolved in 98% cyclopentanone (CPO)) was spin-coated on a COP (cycloolefin polymer) film at 1000 rpm for 10 seconds, dried at 80° C. for 2 minutes, and cured with 250 mJ of UVB. A composition containing a mixture of the dichroic dye and the like of Synthesis Example 1 according to the components and content ratios shown in Table 1 below was dissolved in cyclopentanone at room temperature to prepare a polarizing plate composition solution with a solid content of 26 wt %. Since the reactive liquid crystal itself contains 5 wt % of a curing agent, no separate curing agent was added to the composition.

The polarizing plate composition was spin-coated on the photo-aligned alignment layer at 1000 rpm for 30 seconds. The spin-coated polarizing film-forming composition was then dried at 120° C. for 2 minutes. To photo-crosslink the liquid crystal and dye components, the coating layer was cured under _N2 gas with 250 mJ using a UVB lamp. The cured polarizing plate film had a thickness of 0.9 μm.

Production Example 2
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 2 synthesized in Synthesis Example 2 was used instead of Compound 1 in Synthesis Example 1.

Production Example 3
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 3 synthesized in Synthesis Example 3 was used instead of Compound 1 in Synthesis Example 1.

Production Example 4
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 4 synthesized in Synthesis Example 4 was used instead of Compound 1 in Synthesis Example 1.

Production Example 5
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 5 synthesized in Synthesis Example 5 was used instead of Compound 1 in Synthesis Example 1.

Production Example 6
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 6 synthesized in Synthesis Example 6 was used instead of Compound 1 in Synthesis Example 1.

Production Example 7
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 7 synthesized in Synthesis Example 7 was used instead of Compound 1 in Synthesis Example 1.

Production Example 8
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 8 synthesized in Synthesis Example 8 was used instead of Compound 1 in Synthesis Example 1.

Production Example 9
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 9 synthesized in Synthesis Example 9 was used instead of Compound 1 in Synthesis Example 1.

Production Example 10
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 10 synthesized in Synthesis Example 10 was used instead of Compound 1 in Synthesis Example 1.

Production Example 11
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound 11 synthesized in Synthesis Example 11 was used instead of Compound 1 in Synthesis Example 1.

Comparative Example 1
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound A synthesized in Synthesis Example 12 was used instead of Compound 1 in Synthesis Example 1.

Comparative Example 2
A polarizing plate film was produced in the same manner as in Production Example 1, except that Compound B synthesized in Synthesis Example 13 was used instead of Compound 1 in Synthesis Example 1.
The polarizing plate thus prepared was evaluated for dichroic ratio, heat resistance and light resistance, and the results are shown in Table 2 below.

From Table 2, it can be seen that the polarizing plate of the manufacturing example according to the present invention is better in terms of dichroic ratio, heat resistance, and light resistance than the comparative example.

Claims (15)

A monoazo dichroic dye compound represented by the following chemical formula 1.
In Chemical Formula 1,
R ₁ is any one selected from the group consisting of a substituted or unsubstituted aryl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; any one group selected from the group consisting of NR ₄ OH; NHR ₅ ; NR ₆ ; OR ₇ ; COOR ₈ ; OCOR ₉ ; SR ₁₀ ; a halogen group; OH; CN; COOH; PO ₃ ; SO ₃ ; and NO ₂ , and R ₄ to R ₁₀ are any one selected from the group consisting of a hydrogen atom, an alkoxy group, and an alkoxyalkyl group, each having 1 to 20 carbon atoms; any one of a halogen atom or an alkyl group containing a halogen atom; and any one of a heterocyclic group or an aryl group substituted or unsubstituted with one or more selected from the group consisting of an alkoxy group, an alkoxyalkyl group, a halogen, and an alkyl group;
R ₂ is independently any one selected from the group consisting of hydrogen; a substituted or unsubstituted aryl group having 1 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; NR ₄ OH; NHR ₅ ; NR ₆ ; OR ₇ ; COOR ₈ ; OCOR ₉ ; SR ₁₀ ; a halogen group; OH; CN; COOH; PO ₃ ; SO ₃ ; and NO ₂ , wherein R ₄ to R ₁₀ are independently any one selected from the group consisting of a hydrogen atom, an alkoxy group, and an alkoxyalkyl group; a halogen atom or an alkyl group containing a halogen atom; and a heterocyclic group or an aryl group substituted or unsubstituted with one or more selected from the group consisting of an alkoxy group, an alkoxyalkyl group, a halogen, and an alkyl group;
_X1 and _X2 are each independently any one selected from the group consisting of N, S, O and C;
_Y1 and _Y2 are each independently any one selected from the group consisting of C, S, O, and N;
_R3 is 1,3-indanedione, which is substituted or unsubstituted with any one selected from the group consisting of a substituted or unsubstituted heterocyclic group having 1 to 20 carbon atoms , an alkyl group, an arylalkyl group, an aryl group, a halogen group, an alkoxy group, an alkoxyalkyl group, an alkoxyaryl group, a nitro group , a carboxyl group , and an amide group, or indan or indanone substituted with a cyanoalkyl group . 2. The monoazo dichroic dye compound according to claim 1, wherein _R1 is any one selected from the group consisting of CN, OH, _NHR5 , _NR6 , _OR7 , and _COOR8 , and _R2 is any one selected from the group consisting of hydrogen, CN, OH, _NHR5 , _NR6 , _OR7 , and _COOR8 . 2. The monoazo dichroic dye compound according to claim 1, wherein _R1 is any one selected from the group consisting of _NHR5 , _NR6 , _OR7 , and _COOR8 , and _R2 is any one selected from the group consisting of hydrogen, _NHR5 , _NR6 , _OR7 , and _COOR8 . 2. The monoazo dichroic dye compound according to claim 1, wherein _R1 is _NR6 or _OR7 , and _R2 is any one selected from the group consisting of hydrogen, _OR7 , and _COOR8 . 2. The monoazo dichroic dye compound according to claim 1, wherein _X1 and _X2 are each independently either N or C. The monoazo dichroic dye compound according to claim 1 , wherein Y ₁ and Y ₂ are each independently either S or O. 2. The monoazo dichroic dye compound according to claim 1, wherein _R3 is any one selected from the group consisting of barbituric acid, hydantoin, 3-thiohydantoin , and dihydrouracil, which is substituted or unsubstituted with any one or more selected from the group consisting of alkyl groups , arylalkyl groups, aryl groups, halogen groups, alkoxy groups, alkoxyalkyl groups, alkoxyaryl groups, nitro groups, cyano groups, carboxyl groups, and amide groups; 1,3-indandione, which is substituted or unsubstituted with any one or more selected from the group consisting of alkyl groups, arylalkyl groups, aryl groups, halogen groups, alkoxy groups, alkoxyalkyl groups, alkoxyaryl groups, nitro groups, carboxyl groups, and amide groups; or indan or indanone substituted with a cyanoalkyl group . 2. The monoazo dichroic dye compound according to claim 1, wherein _R3 is any one selected from the group consisting of barbituric acid; hydantoin; and 3-thiohydantoin, which are unsubstituted or substituted with any one or more selected from the group consisting of an alkyl group, an arylalkyl group, and an aryl group. The monoazo dichroic dye compound according to claim 1 , wherein the monoazo dichroic dye compound is any one of compounds represented by the following formulas:
A polarizing plate composition comprising a liquid crystal compound and a dichroic dye compound,
A polarizing plate composition, wherein the dichroic dye compound is the monoazo dichroic dye compound according to claim 1 . A polarizing plate formed by curing the polarizing plate composition according to claim 10. The polarizing plate according to claim 11, wherein the dichroic ratio of the polarizing plate is 19 to 25. The polarizing plate according to claim 11, wherein the heat resistance of the polarizing plate is 6% or less. The polarizing plate according to claim 11, wherein the light resistance of the polarizing plate is 3% or less. An optical element comprising the polarizing plate according to claim 11.